angular 服务之间依赖注入

import { Injectable } from '@angular/core';

@Injectable()
export class LoggerServiceService {

  constructor() { }

  log(message: string) {
    console.log(message);
  }

}

import { Injectable } from '@angular/core';
import { LoggerServiceService } from './logger-service.service';

@Injectable()
export class ProductServiceService {

  constructor(private logger: LoggerServiceService) { }

  getProduct(): Product {
    this.logger.log("iPhone7");
    return new Product(, "iPhone7");
  }

}

export class Product {
  constructor(
    public id: number,
    public title: string
  ) { }
}

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppComponent } from './app.component';
import { Product1Component } from './product1/product1.component';
import { ProductServiceService } from './shared/product-service.service';
import { Product2Component } from './product2/product2.component';
import { LoggerServiceService } from './shared/logger-service.service';

@NgModule({
  declarations: [
    AppComponent,
    Product1Component,
    Product2Component
  ],
  imports: [
    BrowserModule
  ],
  providers: [ProductServiceService,LoggerServiceService],
  bootstrap: [AppComponent]
})
export class AppModule { }